[CPEO-BIF] New NRC report on limitations of sediment dredging at contaminated sites

[bobh@np.craigslist.org]

Sediment dredging has fallen short of achieving cleanup goals at many contaminated
sites

WASHINGTON -- At many projects to dredge contaminated sediments from U.S. rivers
and other bodies of water, it has not been demonstrated that dredging has reduced
the long-term risks the sediments pose to people and wildlife, says a new report
from the National Research Council. Many dredging projects have had difficulty
meeting short-term goals for reducing pollution levels. Whether dredging alone can
reduce long-term risks was difficult to determine at many sites because of
inadequate monitoring data and other limitations, the report says. It calls on the
U.S. Environmental Protection Agency to improve and intensify its monitoring at
dredging and other projects intended to remediate contaminated sediments at the
nation's Superfund sites.

Dredging's ability to achieve cleanup goals depends on a site's characteristics,
the report also concludes. If a particular site has one or more unfavorable
conditions -- the presence of debris such as boulders or cables, for example, or
bedrock lying beneath the contaminated sediment -- then dredging alone is unlikely
to be sufficient. The presence or absence of such conditions should be a major
consideration in deciding whether to dredge at a site, said the committee that
wrote the report.

Contaminated sediments can be found at the bottoms of many U.S. rivers and other
water bodies near former mining, agricultural, or industrial sites. Tainted with
polychlorinated biphenyls (PCBs), heavy metals, or other toxic substances, the
sediments can pose risks to people, fish, and aquatic animals. Many of these sites
are slated for cleanup by EPA under federal Superfund legislation, and a minimum of
14 of them are sediment "megasites" -- sites where the cost of remediating
sediments is expected to reach at least $50 million, or has already done so.
Decisions about whether to dredge at these sites have proved controversial, so
Congress asked the Research Council to evaluate the method's effectiveness. To
inform its conclusions, the committee examined 26 dredging projects, five of them
at megasites, and evaluated whether they had attained their cleanup and
risk-reduction goals.

For the entire article, see:
http://www.eurekalert.org/pub_releases/2007-06/tna-sdh060507.php

Bob Hersh
CPEO


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